The present invention is related to throttle controls for an internal combustion engine, such as a diesel engine. Particularly, the invention concerns throttle controls that have two throttle inputs, each manipulatable by an operator to control the speed of the engine.
In engine driven vehicles, a throttle is manipulated by the vehicle operator to control the speed of the engine, and consequently the speed of the vehicle. In most vehicles, the throttle is in the form of an accelerator foot pedal mounted in the cab of the vehicle. In other applications, the throttle can be a hand throttle, such as the type found on motorcycles. Hand throttles are also used in certain industrial applications, such as hoisting cranes and other heavy-duty industrial machines. In these industrial applications, the engine may drive the machine, such as for a movable crane, as well as a power take-off unit, such as a crane winch.
In recent years, electronic controls have replaced mechanical devices for controlling the operation of the engine. Rather than the direct throttle linkage to a butterfly valve, industrial engines are controlled by more sophisticated engine control modules. These engine control modules, or ECMs, continuously monitor the state of various inputs and apply these inputs to engine control algorithms implemented by on-board microprocessors or computers. One such system for is depicted in FIG. 1. An engine 10 includes a fuel system 12 that controls the intake of air and/or fuel to the various engine cylinders. For example, in a spark ignition engine, the fuel system 12 can include fuel injectors and throttle valves that control the amount of air fed to the engine for combustion. In a typical diesel engine, the fuel system 12 comprises a fuel injector array that controls the amount of diesel fuel introduced into each cylinder. With either type of engine, the speed of the engine 10 is governed by the amount of fuel admitted to the engine cylinders.
The engine speed can be controlled by the operator by way of a throttle 15, which can take the form of a foot pedal or a hand control as described above. In lieu of the direct mechanical linkage to the fuel system, a throttle position signal generator 17 is connected to the throttle 15 to generate a signal in relation to and indicative of the position of the throttle. Typically, the throttle position signal 23 produced by the signal generator 17 is a voltage that increases as the throttle position is increased from an idle position. In the case of a foot pedal, the voltage increases as the pedal is depressed.
The throttle position signal 23 is supplied to an engine control module (ECM) 20, and specifically to a throttle controller 22 within the ECM. In addition to the throttle position signal, the ECM 20 receives signals 26 from various vehicle operating condition sensors 25. These sensors can measure engine parameters, such as exhaust temperature, inlet air pressure, oil pressure and the like, as well as vehicle performance parameters, such as wheel slip. The sensor signals 26 are received by the ECM 20 and used by the throttle controller 22 to derive a signal or signals 27 indicative of a desired engine speed. These signals 27 are fed to an engine speed controller 28 that drives appropriate elements of the fuel system 12. For example, in a diesel engine, the fuel system 12 can include the fuel injector rack, and the engine speed controller 28 can comprise motors driving the injector rack.
Details of a typical throttle system are depicted in FIG. 2. In certain throttle systems, the throttle controller 22 can include an indicator circuit 29 that generates signals indicative of whether the throttle 15 is in a released or a fully depressed position. In throttle systems contemplated by the present invention, the throttle position signal generator 17 includes a potentiometer 30. The potentiometer 30 can be of known design including a resistance element 31 and a wiper 33. The wiper 33 is mechanically connected to the throttle 15 by way of a linkage 35 so that the wiper traverses the resistance element 31 as the throttle is manipulated. A voltage +V is applied at the input to the resistance element 31. The output of the wiper 33 is connected to the throttle signal input 23 to the ECM and throttle controller 22. The throttle signal input 23 is fed to a conditioning circuit 37 so that a voltage is seen at the position signal input 39 that correlates to the throttle position, and ultimately to a requested engine speed. The voltage seen at the position signal input 39 is converted within the throttle controller 22 to a signal usable by the algorithms implemented by the ECM 20 and controller 22.
As mentioned above, certain industrial engine applications utilize a hand controller for an engine throttle control. In many of these applications, both the foot pedal and the hand controller are utilized. Arrangements of this form are typical in construction and agricultural equipment in which the engine drives various power take-off units in addition to the vehicle itself. Prior dual throttle arrangements rely upon the operator to select which throttle input is being used to control the engine speed. One such system is shown in FIG. 3. In this system, two throttles 40, 42 are provided, with one of the throttles constituting a foot pedal and the other a hand controller. Each throttle 40, 42 has its own throttle position signal generator in the form of a separate variable resistance element. Thus, the throttle 40 controls a wiper 45 across a resistance element 44, while the throttle 42 drives wiper 47 along resistance element 46. Both resistance elements are connected a voltage source +V and to a common ground. In this system, an operatormanipulated switch 50 is connected at the throttle signal input 52 that feeds the throttle position signal to the ECM. The switch 50 is movable between node 54 connected to wiper 45 of the first throttle 40, and node 55 connected to wiper 47 of the second throttle 46. With this system, only one throttle provides a voltage signal to the ECM, depending upon the position of switch 50.
While the system depicted in FIG. 3 accommodates the need for multiple throttles in industrial and agricultural applications, it suffers from certain drawbacks. First, the operator must toggle switch 50 to select one of the first and second throttles 40, 42. The switch 50 is a further component that may be subject to deterioration or damage, and may have its performance compromised by vibration or temperature in the vehicle cab.
Most significantly, in dual throttle systems of this type a lag is introduced while the operator switches between throttles. When switching between throttles the operator cannot determine the proper throttle position for the second throttle to match the throttle position of the first throttle. In these circumstances, the operator must release the first throttle 40, flip the switch 50 and then depress the second throttle 42. The operator must then attempt to match the engine speed by depressing the second throttle an appropriate amount. Inevitably, these steps lead to a momentary reduction in engine speed, often followed by over-revving the engine.